The present invention relates to a box beam or girder, particularly for cranes, with lateral web sheets between upper and lower (or top and bottom) flanges and wherein particularly stiffening structures are provided between the side or web sheets.
Box beams or girders of the type to which the invention pertains exhibit the phenomenon that the web or web sheets are subjected to forces tending to create local indent and bulges. However, by putting longitudinal bar-like section pieces on the inside of the "box" and welding them thereto, this kind of deficiency can be avoided. Different loads as far as the moving parts of the crane are concerned, inertia forces generally, and horizontal loads at the flange, all are factors having to do with the introduction of forces into the beam and girder and the general task exists to distribute these forces into and throughout the structure in its entirety. For this one normally provides transversely arranged bulkhead-like bars or sheets being welded to the web sheets and the flanges in the box girder or beam. The manufacture of box girders or beams and being stiffened in that manner is very expensive and requires a large amount of work, particularly for providing and placing the bulkhead-like stiffening sheets